An aircraft without a human pilot on board is known as an Unmanned Aerial Vehicle (UAV), otherwise referred to as a drone. UAVs can be controlled either by an electronic computer located within the aircraft itself or remotely by a navigator or pilot located on the ground or elsewhere, separate from the UAV. UAVs are used for a variety of different purposes including, but not limited to, military operations and surveillance.
Traditional aviation design focuses on many aspects that create a balance of efficiency and performance. The first aspect that is taken into consideration is the center of gravity (CG). The CG is the point at which weight force, or the entire weight of the aircraft, is considered to be concentrated. The CG affects the stability of the entire aircraft and must be kept within certain bounds in order to maintain safety.
To counterbalance the weight force, aircraft generate an opposing force, a lift force, which is generated by the motion of the aircraft as it travels through the air. Another consideration taken into account with aircraft design is the center of lift (CL). The CL is the point at which the lift force is considered to be concentrated.
In most existing aircraft, cargo cannot be placed too far forward or backward in the plane, relative to the CG, because it can create instability. Cargo being transported in the aircraft must be placed within a location very close to the CG, referred to as the CG envelope, usually located around the center portion of the aircraft. The CG envelope can be designated by the manufacturer and takes into account the equipment and contents of the aircraft. This can limit space for transportation to a very small area within the craft.